Various proposals have been made for the provision of thermal insulating materials which, when installed, provide spaced-apart layers - usually of paper or card material - which are faced with a radiation barrier material of the reflective type, usually aluminium foil. Such a material provides insulation by reflecting energy received as radiation. It also has a low emissivity for heat energy received by conduction or convection. The material is usually provided in a folded or rolled compact form which, after unrolling or unfolding, is converted to provide the spaced-apart layers by the pivotal action of in built expanders produced by tensioning the material transversely.
Such materials are described and illustrated in, for example, U.S. Pat. Nos. 4,421,203 and 4,590,727.
The materials are normally used for lining roofs or flooring, being applied for example to lofts. Installation by securing the material to the upper side of the ceiling joists exposed in a loft is a simple matter. Installation on the undersides of ceiling joists is also required in many cases. This involves attaching the material to the vertical faces of the joists so that it is spaced apart from the ceiling. Such spacing is especially necessary when the reflective material of the bottom layer is downwardly facing. If the material contacts the upper side of the ceiling it receives heat by conduction and, since its conductivity is high, makes little or no contribution to the required insulation.